1. Field of the Invention
The present invention relates to electric powered vehicles, such as bicycles, and more particularly, to an electrical control system for an electric powered vehicle.
2. Description of Related Art
Small electric vehicles, such as electric bicycles, have been proposed and used in limited quantities since the early history of motorized vehicles. These electric vehicles have had limited commercial acceptance partially due to their limited features and simple control techniques that have been utilized to control the vehicles. In many cases the control is limited to on, off or multi-position switches that directly apply a battery voltage across a DC motor. The DC motor is directly connected or indirectly connected through a drive system, such as a gear, chain, or roller, to one of the wheels of the vehicle. These switches can connect the motor directly to the battery or they can energize a relay or other switch that will connect the motor to the battery. User accessories are typically controlled in the same manner. Horns and lights have been used on electric vehicles and they are typically controlled using a switch which directly connects the battery voltage to the device. Since these control systems are very simple, they have little or no safety features to protect the motor from overheating or from running away in a short circuit situation. The operation of the control systems also changes as the voltage of the battery changes with temperature or as it is discharged.
Accordingly, it would be very desirable to provide a control system for an electric powered vehicle that overcomes these and other drawbacks of the prior art.
The present invention is directed to a control system for an electric powered vehicle that provides substantially greater control and related features than the simple control systems known in the art. The control system can be utilized with any type of electric powered vehicle, such as bicycles, scooters, tricycles, four-wheeled vehicles, and the like.
In a first embodiment of the invention, the control system maintains an estimate of the temperature of the vehicle electric motor and also an estimate of the amount of heat that is being created in the motor. The continuous rated power level of the motor is defined such that the motor can operate continuously at this level without exceeding its maximum temperature rating. When the motor operates at a lower power level than the continuous rated power level, the temperature of the motor will decrease below the rated maximum temperature. As long as the motor temperature is below the maximum rated temperature, the motor can operate for a short period of time at a higher power level than the continuous rated power level and thereby create a higher amount of heat during that period without exceeding the maximum rated temperature. If the estimate of the amount of heat being dissipated by the motor is lower than the continuous rated power level, the control system acquires heat credits. Conversely, if the estimate of the amount of heat being dissipated by the motor is higher than the continuous rated power level, the control system expends heat credits. The net amount of heat credits in the control system defines how much above the continuous rated power level the motor can operate. As the number of heat credits decreases, the maximum current in the motor is decreased. This provides a smooth continuous degradation of torque to the electric vehicle as the motor heats up when it is pushed beyond its continuous rated power level.
More particularly, the control system includes a motor drive control circuit coupled to the motor and providing a motor drive signal thereto. A throttle control circuit provides a throttle signal to the motor drive control circuit corresponding to a desired speed of the motor. A heat control circuit is electrically connected to the motor and estimates an amount of heat within the motor. The heat control circuit makes a comparison between the estimated amount of heat and a threshold level. The heat control circuit adds heat credits to a baseline amount if the estimated amount of heat is below the threshold level and subtracts heat credits if the estimated amount of heat is above the threshold level. A motor current select circuit provides a motor current signal to the motor drive control circuit. The motor current signal corresponds to the throttle signal if the heat credits exceed the throttle signal, and the motor speed signal is reduced if the heat credits fail to exceed the throttle signal.
In a second embodiment of the invention, the control system monitors the current state of charge of the battery and presents that information to the rider. The state of charge is calculated from the battery voltage. Because the battery voltage varies both with the state of charge and with the amount of current that is being taken out of the battery, the battery is periodically disconnected from the load and put into a state where there is almost no current going into or out of the battery. This allows the battery voltage to be measured in a way that provides an accurate estimate of the state of charge of the battery. More particularly, the control system for an electric powered vehicle comprises a motor, a battery providing a power source for the motor, and a motor drive control circuit coupled to the motor and providing a motor drive signal thereto. A voltage sensing circuit is coupled to the battery and measures a charge state of the battery. The charge sensing circuit additionally provides a control signal to the motor drive control circuit to discontinue the motor drive signal for a period of time sufficient to sample an unloaded voltage output of the battery.
In a third embodiment of the invention, the control system monitors the current operational state of the motor to detect a failure mode in which the full battery voltage is applied to the motor, potentially causing it to run away at full torque and full speed. When a failure mode is detected, the control system first attempts to shut off control signals to the motor. If this fails to stop the failure mode condition, the control system disconnects the battery from the motor by opening a fuse. More particularly, the control system for an electric powered vehicle comprises a motor, a battery providing a power source for the motor, and a motor drive control circuit coupled to the motor and providing a motor drive signal causing the battery to be electrically connected to the motor. A failure mode detect circuit is coupled to the motor to detect a failure mode of the motor. The failure mode detect circuit further comprises two operational states upon detection of the failure mode. The first state is entered upon initial detection of the failure mode of the motor, wherein a first signal is provided to the motor drive control circuit to discontinue providing the motor drive signal. The second state is entered upon continued detection of the failure mode of the motor after a predetermined amount of time following providing the first signal, wherein a second signal is provided to disconnect the battery from the motor.
In a fourth embodiment of the invention, the control system includes a cruise control feature that allows the electric powered vehicle to operate at a desired speed set by the rider. The cruise control function can be disengaged by using the brake or pressing the horn, which are the usual panic responses by the rider. More particularly, the control system for an electric powered vehicle comprises a motor, a battery providing a power source for the motor, a motor drive control circuit coupled to the motor and providing a motor drive signal causing the battery to be electrically connected to the motor, and a throttle control circuit providing a throttle signal to the motor drive control circuit corresponding to a desired speed of the motor. A cruise control circuit is coupled to said throttle control circuit and provides a signal causing the throttle control circuit to lock the throttle signal at a current level. The cruise control circuit is disengaged upon receipt of any one of a horn input, a brake input and a cruise control toggle input.
In a fifth embodiment of the invention, the control system controls operation of vehicle lights to accommodate variations in battery voltage. The control system further comprises a battery, a light control circuit providing a light drive signal to a vehicle light, and a charge sensing circuit coupled to the battery and providing a signal reflecting a charge state of the battery. The light control circuit receives a first input from a light switch and a second input from the charge sensing circuit reflecting the charge state of the battery. The light control circuit modulates the light drive signal in accordance with the second input in order to provide a near constant level of illumination of the light with varying charge level of the battery.
In a sixth embodiment of the invention, the control system controls operation of a horn so that it can also function to provide audible signals reflection operational conditions of the vehicle. The control system further comprising a horn/beeper control circuit providing a horn/beeper drive signal to a horn. The horn/beeper control circuit includes a plurality of predetermined stored waveforms corresponding to respective sounds produced by the horn. The control system can command the horn to generate a desired sound by selecting an appropriate waveform.
In a seventh embodiment of the invention, the control system allows the vehicle to operate in a biofeedback mode to serve as an exercise or training device for the rider. In the biofeedback mode, the control system regulates the amount of power assist provided by the motor to ensure that the rider supplies sufficient physical force to achieve certain fitness goals, such as a desired heart rate or oxygen level. More particularly, the control system comprises a motor coupled to the electric powered vehicle to provide a power assist thereto, a motor drive control circuit coupled to the motor and providing a motor drive signal causing the battery to be electrically connected to the motor, a throttle control circuit providing a throttle signal to the motor drive control circuit corresponding to a desired speed of the motor, and a biofeedback control circuit coupled to the throttle control circuit and providing a signal causing the throttle control circuit to control a magnitude of the power assist to achieve a predetermined physical performance output by a rider of the electric powered vehicle.
A more complete understanding of the electrical system for an electric powered vehicle will be afforded to those skilled in the art, as well as a realization of additional advantages and objects thereof, by a consideration of the following detailed description of the preferred embodiment. Reference will be made to the appended sheets of drawings that which will first be described briefly.